diff --git a/GCryptLib/include/GCrypt/Block.h b/GCryptLib/include/GCrypt/Block.h
index 2184e75..3fefbd5 100644
--- a/GCryptLib/include/GCrypt/Block.h
+++ b/GCryptLib/include/GCrypt/Block.h
@@ -35,8 +35,8 @@ namespace Leonetienne::GCrypt {
       //! Since the matrices values are pretty much sudo-random,
       //! they will most likely integer-overflow.
       //! So see this as a one-way function.
-      Block MMul(const Block& other) const;
-      Block operator*(const Block& other) const;
+      [[nodiscard]] Block MMul(const Block& other) const;
+      [[nodiscard]] Block operator*(const Block& other) const;
 
       //! Will matrix-multiply two blocks together,
       //! and directly write into this same block.
@@ -47,67 +47,98 @@ namespace Leonetienne::GCrypt {
       Block& operator*=(const Block& other);
 
       //! Will xor two blocks together
-      Block Xor(const Block& other) const;
+      [[nodiscard]] Block Xor(const Block& other) const;
       //! Will xor two blocks together
-      Block operator^(const Block& other) const;
+      [[nodiscard]] Block operator^(const Block& other) const;
 
       //! Will xor two blocks together, inplace
       void XorInplace(const Block& other);
       //! Will xor two blocks together, inplace
       Block& operator^=(const Block& other);
 
-      // # TO BE IMPLEMENTED
-      //! Will shift rows upwards by n
-      void ShiftRowsUp(const std::size_t n);
+      //! Will add all the integer making up this block, one by one
+      [[nodiscard]] Block Add(const Block& other) const;
+      //! Will add all the integer making up this block, one by one
+      [[nodiscard]] Block operator+(const Block& other) const;
 
-      // # TO BE IMPLEMENTED
-      //! Will shift matrix rows downwards by n
-      void ShiftRowsDown(const std::size_t n);
+      //! Will add all the integer making up this block, one by one, inplace
+      void AddInplace(const Block& other);
+      //! Will add all the integer making up this block, one by one, inplace
+      Block& operator+=(const Block& other);
 
-      // # TO BE IMPLEMENTED
-      //! Will shift matrix columns to the left by n
-      void ShiftColumnsLeft(const std::size_t n);
+      //! Will subtract all the integer making up this block, one by one
+      [[nodiscard]] Block Sub(const Block& other) const;
+      //! Will subtract all the integer making up this block, one by one
+      [[nodiscard]] Block operator-(const Block& other) const;
 
-      // # TO BE IMPLEMENTED
-      //! Will shift matrix columns to the right by n
-      void ShiftColumnsRight(const std::size_t n);
+      //! Will subtract all the integer making up this block, one by one, inplace
+      void SubInplace(const Block& other);
+      //! Will subtract all the integer making up this block, one by one, inplace
+      Block& operator-=(const Block& other);
 
-      // # TO BE IMPLEMENTED
-      //! Will shift array cells to the left by n
-      void ShiftCellsLeft(const std::size_t n);
+      //! Will shift rows upwards by 1
+      [[nodiscard]] Block ShiftRowsUp() const;
 
-      // # TO BE IMPLEMENTED
-      //! Will shift array cells to the right by n
-      void ShiftCellsRight(const std::size_t n);
+      //! Will shift rows upwards by 1
+      void ShiftRowsUpInplace();
+
+      //! Will shift matrix rows downwards by 1
+      [[nodiscard]] Block ShiftRowsDown() const;
+
+      //! Will shift matrix rows downwards by 1
+      void ShiftRowsDownInplace();
+
+      //! Will shift matrix columns to the left by 1
+      [[nodiscard]] Block ShiftColumnsLeft() const;
+
+      //! Will shift matrix columns to the left by 1
+      void ShiftColumnsLeftInplace();
+
+      //! Will shift matrix columns to the right by 1
+      [[nodiscard]] Block ShiftColumnsRight() const;
+
+      //! Will shift matrix columns to the right by 1
+      void ShiftColumnsRightInplace();
+
+      //! Will shift array cells to the left by 1
+      [[nodiscard]] Block ShiftCellsLeft() const;
+
+      //! Will shift array cells to the left by 1
+      void ShiftCellsLeftInplace();
+
+      //! Will shift array cells to the right by 1
+      [[nodiscard]] Block ShiftCellsRight() const;
+
+      //! Will shift array cells to the right by 1
+      void ShiftCellsRightInplace();
 
       //! Will copy a block
       Block& operator=(const Block& other);
 
       //! Will compare whether or not two blocks are equal
-      bool operator==(const Block& other) const;
+      [[nodiscard]] bool operator==(const Block& other) const;
       //! Will compare whether or not two blocks are unequal
-      bool operator!=(const Block& other) const;
+      [[nodiscard]] bool operator!=(const Block& other) const;
 
       //! Will zero all data
       void Reset();
 
-
       //! Returns 32-bit chunks of data, indexed by matrix coordinates (0-3)
-      std::uint32_t& Get(const std::uint8_t row, const std::uint8_t column);
+      [[nodiscard]] std::uint32_t& Get(const std::uint8_t row, const std::uint8_t column);
       //! Returns 32-bit chunks of data, indexed by matrix coordinates (0-3)
-      const std::uint32_t& Get(const std::uint8_t row, const std::uint8_t column) const;
+      [[nodiscard]] const std::uint32_t& Get(const std::uint8_t row, const std::uint8_t column) const;
 
       //! Returns 32-bit chunks of data, indexed by a 1d-index (0-16)
-      std::uint32_t& Get(const std::uint8_t index);
+      [[nodiscard]] std::uint32_t& Get(const std::uint8_t index);
 
       //! Returns 32-bit chunks of data, indexed by a 1d-index (0-16)
-      const std::uint32_t& Get(const std::uint8_t index) const;
+      [[nodiscard]] const std::uint32_t& Get(const std::uint8_t index) const;
 
       //! Returns 32-bit chunks of data, indexed by a 1d-index (0-16)
-      std::uint32_t& operator[](const std::uint8_t index);
+      [[nodiscard]] std::uint32_t& operator[](const std::uint8_t index);
 
       //! Returns 32-bit chunks of data, indexed by a 1d-index (0-16)
-      const std::uint32_t& operator[](const std::uint8_t index) const;
+      [[nodiscard]] const std::uint32_t& operator[](const std::uint8_t index) const;
 
       static constexpr std::size_t CHUNK_SIZE = sizeof(std::uint32_t);
       static constexpr std::size_t CHUNK_SIZE_BITS = CHUNK_SIZE * 8;
diff --git a/GCryptLib/src/Block.cpp b/GCryptLib/src/Block.cpp
index 0152541..bd16dd1 100644
--- a/GCryptLib/src/Block.cpp
+++ b/GCryptLib/src/Block.cpp
@@ -5,6 +5,10 @@
 #include <cassert>
 #include <cstring>
 
+// Just to be sure, the compiler will optimize this
+// little formula out, let's do it in the preprocessor
+#define MAT_INDEX(row, column) (column*4 + row)
+
 namespace Leonetienne::GCrypt {
 
   Block::Block() {
@@ -132,28 +136,310 @@ namespace Leonetienne::GCrypt {
     return *this;
   }
 
-  void ShiftRowsUp(const std::size_t n) {
-    // TO BE IMPLEMENTED
+  Block Block::Add(const Block& other) const {
+
+    Block m;
+    for (std::size_t i = 0; i < data.size(); i++) {
+      m.Get(i) = this->Get(i) + other.Get(i);
+    }
+    return m;
   }
 
-  void ShiftRowsDown(const std::size_t n) {
-    // TO BE IMPLEMENTED
+  Block Block::operator+(const Block& other) const {
+    return Add(other);
   }
 
-  void ShiftColumnsLeft(const std::size_t n) {
-    // TO BE IMPLEMENTED
+  void Block::AddInplace(const Block& other) {
+    for (std::size_t i = 0; i < data.size(); i++) {
+      this->Get(i) += other.Get(i);
+    }
+    return;
   }
 
-  void ShiftColumnsRight(const std::size_t n) {
-    // TO BE IMPLEMENTED
+  Block& Block::operator+=(const Block& other) {
+    AddInplace(other);
+    return *this;
   }
 
-  void ShiftCellsLeft(const std::size_t n) {
-    // TO BE IMPLEMENTED
+  Block Block::Sub(const Block& other) const {
+
+    Block m;
+    for (std::size_t i = 0; i < data.size(); i++) {
+      m.Get(i) = this->Get(i) - other.Get(i);
+    }
+    return m;
   }
 
-  void ShiftCellsRight(const std::size_t n) {
-    // TO BE IMPLEMENTED
+  Block Block::operator-(const Block& other) const {
+    return Sub(other);
+  }
+
+  void Block::SubInplace(const Block& other) {
+    for (std::size_t i = 0; i < data.size(); i++) {
+      this->Get(i) -= other.Get(i);
+    }
+    return;
+  }
+
+  Block& Block::operator-=(const Block& other) {
+    SubInplace(other);
+    return *this;
+  }
+
+  void Block::ShiftRowsUpInplace() {
+    Block tmp = *this;
+
+    Get(MAT_INDEX(0, 0)) = tmp.Get(MAT_INDEX(1, 0));
+    Get(MAT_INDEX(0, 1)) = tmp.Get(MAT_INDEX(1, 1));
+    Get(MAT_INDEX(0, 2)) = tmp.Get(MAT_INDEX(1, 2));
+    Get(MAT_INDEX(0, 3)) = tmp.Get(MAT_INDEX(1, 3));
+
+    Get(MAT_INDEX(1, 0)) = tmp.Get(MAT_INDEX(2, 0));
+    Get(MAT_INDEX(1, 1)) = tmp.Get(MAT_INDEX(2, 1));
+    Get(MAT_INDEX(1, 2)) = tmp.Get(MAT_INDEX(2, 2));
+    Get(MAT_INDEX(1, 3)) = tmp.Get(MAT_INDEX(2, 3));
+
+    Get(MAT_INDEX(2, 0)) = tmp.Get(MAT_INDEX(3, 0));
+    Get(MAT_INDEX(2, 1)) = tmp.Get(MAT_INDEX(3, 1));
+    Get(MAT_INDEX(2, 2)) = tmp.Get(MAT_INDEX(3, 2));
+    Get(MAT_INDEX(2, 3)) = tmp.Get(MAT_INDEX(3, 3));
+
+    Get(MAT_INDEX(3, 0)) = tmp.Get(MAT_INDEX(0, 0));
+    Get(MAT_INDEX(3, 1)) = tmp.Get(MAT_INDEX(0, 1));
+    Get(MAT_INDEX(3, 2)) = tmp.Get(MAT_INDEX(0, 2));
+    Get(MAT_INDEX(3, 3)) = tmp.Get(MAT_INDEX(0, 3));
+
+    return;
+  }
+
+  Block Block::ShiftRowsUp() const {
+    Block b;
+
+    b.Get(MAT_INDEX(0, 0)) = Get(MAT_INDEX(1, 0));
+    b.Get(MAT_INDEX(0, 1)) = Get(MAT_INDEX(1, 1));
+    b.Get(MAT_INDEX(0, 2)) = Get(MAT_INDEX(1, 2));
+    b.Get(MAT_INDEX(0, 3)) = Get(MAT_INDEX(1, 3));
+
+    b.Get(MAT_INDEX(1, 0)) = Get(MAT_INDEX(2, 0));
+    b.Get(MAT_INDEX(1, 1)) = Get(MAT_INDEX(2, 1));
+    b.Get(MAT_INDEX(1, 2)) = Get(MAT_INDEX(2, 2));
+    b.Get(MAT_INDEX(1, 3)) = Get(MAT_INDEX(2, 3));
+
+    b.Get(MAT_INDEX(2, 0)) = Get(MAT_INDEX(3, 0));
+    b.Get(MAT_INDEX(2, 1)) = Get(MAT_INDEX(3, 1));
+    b.Get(MAT_INDEX(2, 2)) = Get(MAT_INDEX(3, 2));
+    b.Get(MAT_INDEX(2, 3)) = Get(MAT_INDEX(3, 3));
+
+    b.Get(MAT_INDEX(3, 0)) = Get(MAT_INDEX(0, 0));
+    b.Get(MAT_INDEX(3, 1)) = Get(MAT_INDEX(0, 1));
+    b.Get(MAT_INDEX(3, 2)) = Get(MAT_INDEX(0, 2));
+    b.Get(MAT_INDEX(3, 3)) = Get(MAT_INDEX(0, 3));
+
+    return b;
+  }
+
+  void Block::ShiftRowsDownInplace() {
+    Block tmp = *this;
+
+    Get(MAT_INDEX(0, 0)) = tmp.Get(MAT_INDEX(3, 0));
+    Get(MAT_INDEX(0, 1)) = tmp.Get(MAT_INDEX(3, 1));
+    Get(MAT_INDEX(0, 2)) = tmp.Get(MAT_INDEX(3, 2));
+    Get(MAT_INDEX(0, 3)) = tmp.Get(MAT_INDEX(3, 3));
+
+    Get(MAT_INDEX(1, 0)) = tmp.Get(MAT_INDEX(0, 0));
+    Get(MAT_INDEX(1, 1)) = tmp.Get(MAT_INDEX(0, 1));
+    Get(MAT_INDEX(1, 2)) = tmp.Get(MAT_INDEX(0, 2));
+    Get(MAT_INDEX(1, 3)) = tmp.Get(MAT_INDEX(0, 3));
+
+    Get(MAT_INDEX(2, 0)) = tmp.Get(MAT_INDEX(1, 0));
+    Get(MAT_INDEX(2, 1)) = tmp.Get(MAT_INDEX(1, 1));
+    Get(MAT_INDEX(2, 2)) = tmp.Get(MAT_INDEX(1, 2));
+    Get(MAT_INDEX(2, 3)) = tmp.Get(MAT_INDEX(1, 3));
+
+    Get(MAT_INDEX(3, 0)) = tmp.Get(MAT_INDEX(2, 0));
+    Get(MAT_INDEX(3, 1)) = tmp.Get(MAT_INDEX(2, 1));
+    Get(MAT_INDEX(3, 2)) = tmp.Get(MAT_INDEX(2, 2));
+    Get(MAT_INDEX(3, 3)) = tmp.Get(MAT_INDEX(2, 3));
+
+    return;
+  }
+
+  Block Block::ShiftRowsDown() const {
+    Block b;
+
+    b.Get(MAT_INDEX(0, 0)) = Get(MAT_INDEX(3, 0));
+    b.Get(MAT_INDEX(0, 1)) = Get(MAT_INDEX(3, 1));
+    b.Get(MAT_INDEX(0, 2)) = Get(MAT_INDEX(3, 2));
+    b.Get(MAT_INDEX(0, 3)) = Get(MAT_INDEX(3, 3));
+
+    b.Get(MAT_INDEX(1, 0)) = Get(MAT_INDEX(0, 0));
+    b.Get(MAT_INDEX(1, 1)) = Get(MAT_INDEX(0, 1));
+    b.Get(MAT_INDEX(1, 2)) = Get(MAT_INDEX(0, 2));
+    b.Get(MAT_INDEX(1, 3)) = Get(MAT_INDEX(0, 3));
+
+    b.Get(MAT_INDEX(2, 0)) = Get(MAT_INDEX(1, 0));
+    b.Get(MAT_INDEX(2, 1)) = Get(MAT_INDEX(1, 1));
+    b.Get(MAT_INDEX(2, 2)) = Get(MAT_INDEX(1, 2));
+    b.Get(MAT_INDEX(2, 3)) = Get(MAT_INDEX(1, 3));
+
+    b.Get(MAT_INDEX(3, 0)) = Get(MAT_INDEX(2, 0));
+    b.Get(MAT_INDEX(3, 1)) = Get(MAT_INDEX(2, 1));
+    b.Get(MAT_INDEX(3, 2)) = Get(MAT_INDEX(2, 2));
+    b.Get(MAT_INDEX(3, 3)) = Get(MAT_INDEX(2, 3));
+
+    return b;
+  }
+
+  void Block::ShiftColumnsLeftInplace() {
+    Block tmp = *this;
+
+    Get(MAT_INDEX(0, 0)) = tmp.Get(MAT_INDEX(0, 1));
+    Get(MAT_INDEX(1, 0)) = tmp.Get(MAT_INDEX(1, 1));
+    Get(MAT_INDEX(2, 0)) = tmp.Get(MAT_INDEX(2, 1));
+    Get(MAT_INDEX(3, 0)) = tmp.Get(MAT_INDEX(3, 1));
+
+    Get(MAT_INDEX(0, 1)) = tmp.Get(MAT_INDEX(0, 2));
+    Get(MAT_INDEX(1, 1)) = tmp.Get(MAT_INDEX(1, 2));
+    Get(MAT_INDEX(2, 1)) = tmp.Get(MAT_INDEX(2, 2));
+    Get(MAT_INDEX(3, 1)) = tmp.Get(MAT_INDEX(3, 2));
+
+    Get(MAT_INDEX(0, 2)) = tmp.Get(MAT_INDEX(0, 3));
+    Get(MAT_INDEX(1, 2)) = tmp.Get(MAT_INDEX(1, 3));
+    Get(MAT_INDEX(2, 2)) = tmp.Get(MAT_INDEX(2, 3));
+    Get(MAT_INDEX(3, 2)) = tmp.Get(MAT_INDEX(3, 3));
+
+    Get(MAT_INDEX(0, 3)) = tmp.Get(MAT_INDEX(0, 0));
+    Get(MAT_INDEX(1, 3)) = tmp.Get(MAT_INDEX(1, 0));
+    Get(MAT_INDEX(2, 3)) = tmp.Get(MAT_INDEX(2, 0));
+    Get(MAT_INDEX(3, 3)) = tmp.Get(MAT_INDEX(3, 0));
+
+    return;
+  }
+
+  Block Block::ShiftColumnsLeft() const {
+    Block b;
+
+    b.Get(MAT_INDEX(0, 0)) = Get(MAT_INDEX(0, 1));
+    b.Get(MAT_INDEX(1, 0)) = Get(MAT_INDEX(1, 1));
+    b.Get(MAT_INDEX(2, 0)) = Get(MAT_INDEX(2, 1));
+    b.Get(MAT_INDEX(3, 0)) = Get(MAT_INDEX(3, 1));
+
+    b.Get(MAT_INDEX(0, 1)) = Get(MAT_INDEX(0, 2));
+    b.Get(MAT_INDEX(1, 1)) = Get(MAT_INDEX(1, 2));
+    b.Get(MAT_INDEX(2, 1)) = Get(MAT_INDEX(2, 2));
+    b.Get(MAT_INDEX(3, 1)) = Get(MAT_INDEX(3, 2));
+
+    b.Get(MAT_INDEX(0, 2)) = Get(MAT_INDEX(0, 3));
+    b.Get(MAT_INDEX(1, 2)) = Get(MAT_INDEX(1, 3));
+    b.Get(MAT_INDEX(2, 2)) = Get(MAT_INDEX(2, 3));
+    b.Get(MAT_INDEX(3, 2)) = Get(MAT_INDEX(3, 3));
+
+    b.Get(MAT_INDEX(0, 3)) = Get(MAT_INDEX(0, 0));
+    b.Get(MAT_INDEX(1, 3)) = Get(MAT_INDEX(1, 0));
+    b.Get(MAT_INDEX(2, 3)) = Get(MAT_INDEX(2, 0));
+    b.Get(MAT_INDEX(3, 3)) = Get(MAT_INDEX(3, 0));
+
+    return b;
+  }
+
+  void Block::ShiftColumnsRightInplace() {
+    Block tmp = *this;
+
+    Get(MAT_INDEX(0, 1)) = tmp.Get(MAT_INDEX(0, 0));
+    Get(MAT_INDEX(1, 1)) = tmp.Get(MAT_INDEX(1, 0));
+    Get(MAT_INDEX(2, 1)) = tmp.Get(MAT_INDEX(2, 0));
+    Get(MAT_INDEX(3, 1)) = tmp.Get(MAT_INDEX(3, 0));
+
+    Get(MAT_INDEX(0, 2)) = tmp.Get(MAT_INDEX(0, 1));
+    Get(MAT_INDEX(1, 2)) = tmp.Get(MAT_INDEX(1, 1));
+    Get(MAT_INDEX(2, 2)) = tmp.Get(MAT_INDEX(2, 1));
+    Get(MAT_INDEX(3, 2)) = tmp.Get(MAT_INDEX(3, 1));
+
+    Get(MAT_INDEX(0, 3)) = tmp.Get(MAT_INDEX(0, 2));
+    Get(MAT_INDEX(1, 3)) = tmp.Get(MAT_INDEX(1, 2));
+    Get(MAT_INDEX(2, 3)) = tmp.Get(MAT_INDEX(2, 2));
+    Get(MAT_INDEX(3, 3)) = tmp.Get(MAT_INDEX(3, 2));
+
+    Get(MAT_INDEX(0, 0)) = tmp.Get(MAT_INDEX(0, 3));
+    Get(MAT_INDEX(1, 0)) = tmp.Get(MAT_INDEX(1, 3));
+    Get(MAT_INDEX(2, 0)) = tmp.Get(MAT_INDEX(2, 3));
+    Get(MAT_INDEX(3, 0)) = tmp.Get(MAT_INDEX(3, 3));
+
+    return;
+  }
+
+  Block Block::ShiftColumnsRight() const {
+    Block b;
+
+    b.Get(MAT_INDEX(0, 1)) = Get(MAT_INDEX(0, 0));
+    b.Get(MAT_INDEX(1, 1)) = Get(MAT_INDEX(1, 0));
+    b.Get(MAT_INDEX(2, 1)) = Get(MAT_INDEX(2, 0));
+    b.Get(MAT_INDEX(3, 1)) = Get(MAT_INDEX(3, 0));
+
+    b.Get(MAT_INDEX(0, 2)) = Get(MAT_INDEX(0, 1));
+    b.Get(MAT_INDEX(1, 2)) = Get(MAT_INDEX(1, 1));
+    b.Get(MAT_INDEX(2, 2)) = Get(MAT_INDEX(2, 1));
+    b.Get(MAT_INDEX(3, 2)) = Get(MAT_INDEX(3, 1));
+
+    b.Get(MAT_INDEX(0, 3)) = Get(MAT_INDEX(0, 2));
+    b.Get(MAT_INDEX(1, 3)) = Get(MAT_INDEX(1, 2));
+    b.Get(MAT_INDEX(2, 3)) = Get(MAT_INDEX(2, 2));
+    b.Get(MAT_INDEX(3, 3)) = Get(MAT_INDEX(3, 2));
+
+    b.Get(MAT_INDEX(0, 0)) = Get(MAT_INDEX(0, 3));
+    b.Get(MAT_INDEX(1, 0)) = Get(MAT_INDEX(1, 3));
+    b.Get(MAT_INDEX(2, 0)) = Get(MAT_INDEX(2, 3));
+    b.Get(MAT_INDEX(3, 0)) = Get(MAT_INDEX(3, 3));
+
+    return b;
+  }
+
+  void Block::ShiftCellsLeftInplace() {
+    Block tmp = *this;
+
+    Get(15) = tmp.Get(0);
+
+    for (std::size_t i = 0; i < 15; i++) {
+      Get(i) = tmp.Get(i+1);
+    }
+
+    return;
+  }
+
+  Block Block::ShiftCellsLeft() const {
+    Block b;
+
+    b.Get(15) = Get(0);
+
+    for (std::size_t i = 0; i < 15; i++) {
+      b.Get(i) = Get(i+1);
+    }
+
+    return b;
+  }
+
+  void Block::ShiftCellsRightInplace() {
+    Block tmp = *this;
+
+    Get(0) = tmp.Get(15);
+
+    for (std::size_t i = 1; i < 16; i++) {
+      Get(i) = tmp.Get(i-1);
+    }
+
+    return;
+  }
+
+  Block Block::ShiftCellsRight() const {
+    Block b;
+
+    b.Get(0) = Get(15);
+
+    for (std::size_t i = 1; i < 16; i++) {
+      b.Get(i) = Get(i-1);
+    }
+
+    return b;
   }
 
   Block& Block::operator=(const Block& other) {
@@ -162,11 +448,11 @@ namespace Leonetienne::GCrypt {
   }
 
   std::uint32_t& Block::Get(const std::uint8_t row, const std::uint8_t column){
-    return data[column*4 + row];
+    return data[MAT_INDEX(row, column)];
   }
 
   const std::uint32_t& Block::Get(const std::uint8_t row, const std::uint8_t column) const {
-    return data[column*4 + row];
+    return data[MAT_INDEX(row, column)];
   }
 
   std::uint32_t& Block::Get(const std::uint8_t index) {
@@ -222,3 +508,5 @@ namespace Leonetienne::GCrypt {
 
 }
 
+#undef MAT_INDEX
+
diff --git a/GCryptLib/src/Feistel.cpp b/GCryptLib/src/Feistel.cpp
index 565d54a..9f2d20d 100644
--- a/GCryptLib/src/Feistel.cpp
+++ b/GCryptLib/src/Feistel.cpp
@@ -1,7 +1,6 @@
 #include <unordered_map>
 #include "GCrypt/Feistel.h"
 #include "GCrypt/Util.h"
-#include "GCrypt/BlockMatrix.h"
 #include "GCrypt/Config.h"
 
 namespace Leonetienne::GCrypt {
diff --git a/GCryptLib/test/Block.cpp b/GCryptLib/test/Block.cpp
index faa715e..09730f7 100644
--- a/GCryptLib/test/Block.cpp
+++ b/GCryptLib/test/Block.cpp
@@ -1,4 +1,5 @@
 #include <GCrypt/Block.h>
+#include <GCrypt/Key.h>
 #include "Catch2.h"
 #include <cstdlib>
 #include <time.h>
@@ -148,6 +149,116 @@ TEST_CASE(__FILE__"/operator^&=", "[Block]") {
   REQUIRE(block1 == block3);
 }
 
+// Tests that operator+ (add) works
+TEST_CASE(__FILE__"/add", "[Block]") {
+
+  // Setup
+  Block block;
+  for (std::size_t i = 0; i < 16; i++) {
+    block.Get(i) = i * 1024;
+  }
+
+  Block addRH;
+  for (std::size_t i = 0; i < 16; i++) {
+    addRH.Get(i) = i * 5099;
+  }
+
+  // Exercise
+  Block result = block + addRH;
+
+  Block manualResult;
+  for (std::size_t i = 0; i < 16; i++) {
+    manualResult.Get(i) = (i * 1024) + (i * 5099);
+  }
+
+  // Verify
+  REQUIRE(result == manualResult);
+}
+
+// Tests that operator+ is the same as +=
+TEST_CASE(__FILE__"/operator+&=", "[Block]") {
+
+  // Setup
+  Block block1;
+  for (std::size_t i = 0; i < 16; i++) {
+    block1.Get(i) = i * 1024;
+  }
+
+  Block block2;
+  for (std::size_t i = 0; i < 16; i++) {
+    block2.Get(i) = i * 5099 * 2;
+  }
+
+  // Exercise
+  Block block3 = block1 + block2;
+  block1 += block2;
+
+  // Verify
+  REQUIRE(block1 == block3);
+}
+
+// Tests that operator- (subtract) works
+TEST_CASE(__FILE__"/subtract", "[Block]") {
+
+  // Setup
+  Block block;
+  for (std::size_t i = 0; i < 16; i++) {
+    block.Get(i) = i * 1024;
+  }
+
+  Block subRH;
+  for (std::size_t i = 0; i < 16; i++) {
+    subRH.Get(i) = i * 5099;
+  }
+
+  // Exercise
+  Block result = block - subRH;
+
+  Block manualResult;
+  for (std::size_t i = 0; i < 16; i++) {
+    manualResult.Get(i) = (i * 1024) - (i * 5099);
+  }
+
+  // Verify
+  REQUIRE(result == manualResult);
+}
+
+// Tests that operator- is the same as -=
+TEST_CASE(__FILE__"/operator-&=", "[Block]") {
+
+  // Setup
+  Block block1;
+  for (std::size_t i = 0; i < 16; i++) {
+    block1.Get(i) = i * 1024;
+  }
+
+  Block block2;
+  for (std::size_t i = 0; i < 16; i++) {
+    block2.Get(i) = i * 5099 * 2;
+  }
+
+  // Exercise
+  Block block3 = block1 - block2;
+  block1 -= block2;
+
+  // Verify
+  REQUIRE(block1 == block3);
+}
+
+// Tests that subtraction undoes addition, and vica versa
+TEST_CASE(__FILE__"/subtraction-undoes-addition", "[Block]") {
+  // Setup
+  const Block a = Key::FromPassword("Halleluja");
+  const Block b = Key::FromPassword("Ananas");
+
+  // Exercise
+  const Block a_plus_b = a + b;
+  const Block a_plus_b_minus_b = a_plus_b - b;
+
+  // Verify
+  REQUIRE(a == a_plus_b_minus_b);
+}
+
 // Tests that operator== works correctly
 TEST_CASE(__FILE__"/operator==", "[Block]") {
 
@@ -249,3 +360,276 @@ TEST_CASE(__FILE__"/reset", "[Block]") {
     REQUIRE(block[i] == 0);
   }
 }
+
+// Tests that shift rows up works
+TEST_CASE(__FILE__"/shift-rows-up", "[Block]") {
+
+  // Setup
+  Block a;
+  a.Get(0,0) = 10; a.Get(0,1) = 11; a.Get(0,2) = 12; a.Get(0,3) = 13;
+  a.Get(1,0) = 20; a.Get(1,1) = 21; a.Get(1,2) = 22; a.Get(1,3) = 23;
+  a.Get(2,0) = 30; a.Get(2,1) = 31; a.Get(2,2) = 32; a.Get(2,3) = 33;
+  a.Get(3,0) = 40; a.Get(3,1) = 41; a.Get(3,2) = 42; a.Get(3,3) = 43;
+
+  Block e; /* expected */
+  e.Get(0,0) = 20; e.Get(0,1) = 21; e.Get(0,2) = 22; e.Get(0,3) = 23;
+  e.Get(1,0) = 30; e.Get(1,1) = 31; e.Get(1,2) = 32; e.Get(1,3) = 33;
+  e.Get(2,0) = 40; e.Get(2,1) = 41; e.Get(2,2) = 42; e.Get(2,3) = 43;
+  e.Get(3,0) = 10; e.Get(3,1) = 11; e.Get(3,2) = 12; e.Get(3,3) = 13;
+
+  // Exercise
+  a.ShiftRowsUpInplace();
+
+  // Verify
+  REQUIRE(a == e);
+}
+
+// Tests that ShiftRowsUpInplace() does the exact same thing as ShiftRowsUp()
+TEST_CASE(__FILE__"/shift-rows-up-same-as-inplace", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  const Block initial_a = a;
+
+  // Exercise and verify
+  a.ShiftRowsUpInplace();
+  REQUIRE(a == initial_a.ShiftRowsUp());
+}
+
+// Tests that shift rows down works
+TEST_CASE(__FILE__"/shift-rows-down", "[Block]") {
+
+  // Setup
+  Block a;
+  a.Get(0,0) = 10; a.Get(0,1) = 11; a.Get(0,2) = 12; a.Get(0,3) = 13;
+  a.Get(1,0) = 20; a.Get(1,1) = 21; a.Get(1,2) = 22; a.Get(1,3) = 23;
+  a.Get(2,0) = 30; a.Get(2,1) = 31; a.Get(2,2) = 32; a.Get(2,3) = 33;
+  a.Get(3,0) = 40; a.Get(3,1) = 41; a.Get(3,2) = 42; a.Get(3,3) = 43;
+
+  Block e; /* expected */
+  e.Get(0,0) = 40; e.Get(0,1) = 41; e.Get(0,2) = 42; e.Get(0,3) = 43;
+  e.Get(1,0) = 10; e.Get(1,1) = 11; e.Get(1,2) = 12; e.Get(1,3) = 13;
+  e.Get(2,0) = 20; e.Get(2,1) = 21; e.Get(2,2) = 22; e.Get(2,3) = 23;
+  e.Get(3,0) = 30; e.Get(3,1) = 31; e.Get(3,2) = 32; e.Get(3,3) = 33;
+
+  // Exercise
+  a.ShiftRowsDownInplace();
+
+  // Verify
+  REQUIRE(a == e);
+}
+
+// Tests that ShiftRowsDownInplace() does the exact same thing as ShiftRowsDown()
+TEST_CASE(__FILE__"/shift-rows-down-same-as-inplace", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  const Block initial_a = a;
+
+  // Exercise and verify
+  a.ShiftRowsDownInplace();
+  REQUIRE(a == initial_a.ShiftRowsDown());
+}
+
+// Tests that shift columns left works
+TEST_CASE(__FILE__"/shift-columns-left", "[Block]") {
+
+  // Setup
+  Block a;
+  a.Get(0,0) = 10; a.Get(0,1) = 11; a.Get(0,2) = 12; a.Get(0,3) = 13;
+  a.Get(1,0) = 20; a.Get(1,1) = 21; a.Get(1,2) = 22; a.Get(1,3) = 23;
+  a.Get(2,0) = 30; a.Get(2,1) = 31; a.Get(2,2) = 32; a.Get(2,3) = 33;
+  a.Get(3,0) = 40; a.Get(3,1) = 41; a.Get(3,2) = 42; a.Get(3,3) = 43;
+
+  Block e; /* expected */
+  e.Get(0,0) = 11; e.Get(0,1) = 12; e.Get(0,2) = 13; e.Get(0,3) = 10;
+  e.Get(1,0) = 21; e.Get(1,1) = 22; e.Get(1,2) = 23; e.Get(1,3) = 20;
+  e.Get(2,0) = 31; e.Get(2,1) = 32; e.Get(2,2) = 33; e.Get(2,3) = 30;
+  e.Get(3,0) = 41; e.Get(3,1) = 42; e.Get(3,2) = 43; e.Get(3,3) = 40;
+
+  // Exercise
+  a.ShiftColumnsLeftInplace();
+
+  // Verify
+  REQUIRE(a == e);
+}
+
+// Tests that ShiftColumnsLeftInplace()() does the exact same thing as ShiftColumnsLeft()
+TEST_CASE(__FILE__"/shift-columns-left-same-as-inplace", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  const Block initial_a = a;
+
+  // Exercise and verify
+  a.ShiftColumnsLeftInplace();
+  REQUIRE(a == initial_a.ShiftColumnsLeft());
+}
+
+// Tests that shift columns right works
+TEST_CASE(__FILE__"/shift-columns-right", "[Block]") {
+
+  // Setup
+  Block a;
+  a.Get(0,0) = 10; a.Get(0,1) = 11; a.Get(0,2) = 12; a.Get(0,3) = 13;
+  a.Get(1,0) = 20; a.Get(1,1) = 21; a.Get(1,2) = 22; a.Get(1,3) = 23;
+  a.Get(2,0) = 30; a.Get(2,1) = 31; a.Get(2,2) = 32; a.Get(2,3) = 33;
+  a.Get(3,0) = 40; a.Get(3,1) = 41; a.Get(3,2) = 42; a.Get(3,3) = 43;
+
+  Block e; /* expected */
+  e.Get(0,0) = 13; e.Get(0,1) = 10; e.Get(0,2) = 11; e.Get(0,3) = 12;
+  e.Get(1,0) = 23; e.Get(1,1) = 20; e.Get(1,2) = 21; e.Get(1,3) = 22;
+  e.Get(2,0) = 33; e.Get(2,1) = 30; e.Get(2,2) = 31; e.Get(2,3) = 32;
+  e.Get(3,0) = 43; e.Get(3,1) = 40; e.Get(3,2) = 41; e.Get(3,3) = 42;
+
+  // Exercise
+  a.ShiftColumnsRightInplace();
+
+  // Verify
+  REQUIRE(a == e);
+}
+
+// Tests that ShiftColumnsRightInplace()() does the exact same thing as ShiftColumnsRight()
+TEST_CASE(__FILE__"/shift-columns-right-same-as-inplace", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  const Block initial_a = a;
+
+  // Exercise and verify
+  a.ShiftColumnsRightInplace();
+  REQUIRE(a == initial_a.ShiftColumnsRight());
+}
+
+// Tests that shift cells left works
+TEST_CASE(__FILE__"/shift-cells-left", "[Block]") {
+
+  // Setup
+  Block a;
+  for (std::size_t i = 0; i < 16; i++) {
+    a.Get(i) = i;
+  }
+
+  Block expected;
+  for (std::size_t i = 0; i < 15; i++) {
+    expected.Get(i) = i+1;
+  }
+  expected.Get(15) = 0;
+
+  // Exercise
+  a.ShiftCellsLeftInplace();
+
+  // Verify
+  REQUIRE(a == expected);
+}
+
+// Tests that ShiftCellsLeftInplace()() does the exact same thing as ShiftCellsLeft()
+TEST_CASE(__FILE__"/shift-cells-left-same-as-inplace", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  const Block initial_a = a;
+
+  // Exercise and verify
+  a.ShiftCellsLeftInplace();
+  REQUIRE(a == initial_a.ShiftCellsLeft());
+}
+
+// Tests that shift cells right works
+TEST_CASE(__FILE__"/shift-cells-right", "[Block]") {
+
+  // Setup
+  Block a;
+  for (std::size_t i = 0; i < 16; i++) {
+    a.Get(i) = i;
+  }
+
+  Block expected;
+  for (std::size_t i = 1; i < 16; i++) {
+    expected.Get(i) = i-1;
+  }
+  expected.Get(0) = 15;
+
+  // Exercise
+  a.ShiftCellsRightInplace();
+
+  // Verify
+  REQUIRE(a == expected);
+}
+
+// Tests that ShiftCellsRightInplace()() does the exact same thing as ShiftCellsRight()
+TEST_CASE(__FILE__"/shift-cells-right-same-as-inplace", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  const Block initial_a = a;
+
+  // Exercise and verify
+  a.ShiftCellsRightInplace();
+  REQUIRE(a == initial_a.ShiftCellsRight());
+}
+
+// Tests that shifting down undoes shifting up, and vica versa
+TEST_CASE(__FILE__"/shift-down-undoes-shift-up", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  const Block initial_a = a;
+
+  // Exercise
+  a.ShiftRowsUpInplace();
+  a.ShiftRowsDownInplace();
+
+  // Verify
+  REQUIRE(a == initial_a);
+}
+
+// Tests that shifting left undoes shifting right, and vica versa
+TEST_CASE(__FILE__"/shift-left-undoes-shift-right", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  const Block initial_a = a;
+
+  // Exercise
+  a.ShiftColumnsRightInplace();
+  a.ShiftColumnsLeftInplace();
+
+  // Verify
+  REQUIRE(a == initial_a);
+}
+
+// Tests that shifting cells left undoes shifting cells right, and vica versa
+TEST_CASE(__FILE__"/cellshift-left-undoes-cellshift-right", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  const Block initial_a = a;
+
+  // Exercise
+  a.ShiftCellsRightInplace();
+  a.ShiftCellsLeftInplace();
+
+  // Verify
+  REQUIRE(a == initial_a);
+}
+
+// Tests that multiple, combined shifts and additions can be undone
+TEST_CASE(__FILE__"/multiple-combined-shifts-and-additions-can-be-undone", "[Block]") {
+  // Setup
+  Block a = Key::FromPassword("Halleluja");
+  Block key = Key::FromPassword("Papaya");
+
+  const Block initial_a = a;
+
+  // Exercise (mix-up)
+  for (std::size_t i = 0; i < 64; i++) {
+    a.ShiftRowsUpInplace();
+    a.ShiftColumnsLeftInplace();
+    a += key;
+    a.ShiftCellsRightInplace();
+  }
+
+  // Exercise (un-mix)
+  for (std::size_t i = 0; i < 64; i++) {
+    a.ShiftCellsLeftInplace();
+    a -= key;
+    a.ShiftColumnsRightInplace();
+    a.ShiftRowsDownInplace();
+  }
+
+  // Verify
+  REQUIRE(a == initial_a);
+}
+